Automated and semi-automated water irrigation systems are usually operated by a programmable timer/controller to open and close water valves through which the water passes to the irrigation system. Such timer/controllers are capable of opening and closing a number of water valves at pre-set times and for selected durations to water lawns and gardens. Each water valve typically controls the supply of water to a number of sprinkler heads that irrigate a section of the lawn and garden area to be irrigated. Normally, a single irrigation system will include a number of such water valves that are operated by the timer/controller to irrigate each section of the overall system on a desired schedule. In the past, the programmable timer/controller has been powered by a 120 volt alternating current (AC) power source.
The water valves are opened and closed by means of a diaphragm, controlled by the actuator of a solenoid. To open the valve, the programmable timer/controller supplies current to the solenoid, causing the actuator to pop up and open the valve. The actuator is spring-loaded so that, when the solenoid is not supplied with current, it returns to its original position and causes the valve to close. An alternating current source is preferred because it conveniently provides the continuous supply of current required to keep the section valves open during irrigation.
Use of such AC timer/controllers in many remote areas is, however, extremely costly and inconvenient because, in such areas, an AC power line usually must also be installed. Typical of such remote areas are medians of roadways, farms, parks and the like. To meet the need for a programmable timer/controller usable in remote areas without a 120 volt AC power source, IRRI-TROL Corporation, located at 27940 Beale Court, Valencia, Calif. 91355 developed two models of battery-operated controllers. The first model, identified by the trademark "CQ/DC," was later replaced by a successor battery-operated controller, identified by the trademark "IBOC." Power was supplied to both models by a 24 volt DC power source installed at the remote location. The 24 volt DC power source usually comprises two 12 volt batteries connected in series.
The battery-operated controllers could not be used with the spring-loaded solenoids of the AC powered controllers, because such solenoids require a continuous current supply when actuated. Such a current demand would quickly consume the supply of the battery power. Thus, valves of systems utilizing the battery-operated controllers are actuated by a latching solenoid, rather than the spring-loaded solenoids.
The latching solenoid eliminated the need for a continuous current to control the position of the section valves. When a positive 24 volt pulse of relatively short duration is supplied by the CQ/DC or IBOC controllers, the solenoid actuator retracts and latches, thereby opening the water valve. The water valve thereafter remains open without any additional current being supplied by the controller. Conversely, a negative 24 volt pulse from the controller unlatches the actuator and permits the valve to be closed.
Use of the IBOC and CQ/DC controllers in combination with latching solenoids unexpectedly resulted in one or more section valves remaining open after the watering cycle had ended, thereby allowing watering to continue indefinitely. This caused damage from flooding and freezing, in addition to wasting water. This malfunction occurs in systems which utilize, as is typical, rain and/or freeze sensors, or any other climatic condition sensors, to prevent watering when it rains or when the temperature is below freezing. Freeze sensors are desirable, for example, if the water sprinkler system is installed in a roadway median, to prevent the system from operating in freezing conditions that would form hazardous ice on the adjacent roadway. Rain sensors are desirable to avoid over-watering and to save water. Such sensors disable the control circuit between the controller and the latching solenoids, to prevent the valves from being opened at the start of a planned watering cycle.
Upon close examination of these failures, it was found that the rain or freeze sensors had activated when one or more section water valves were open, thereby disabling the control circuit to each valve. Hence, the controller could not shut the water valve. This exacerbated the very problems of freezing, flooding and water waste that the sensors are designed to avoid. Because the only commercially available rain and freeze sensors employ this method of opening the control circuit, there is a great need for an apparatus and method for avoiding disablement of the control circuit by the sensors in the midst of a watering cycle.